A knowledge of ocean currents, their locations and rates, is important for various purposes including meteorology, oceanography, fisheries and navigation among others. One scientifically acceptable and customary method of collecting information used to improve our knowledge of ocean currents involves tracking currents with floating instrumentation, usually called drifters.
The accurate analysis of ocean currents by this method requires a great many drifters tracked over long time periods up to several years. Rapid progress can be made only if this method is economical, which requires low cost drifters having useful lives greater than one year. Long life in turn requires efficient use of energy consuming components such as transmitters, and resistance to damage from waves, fish, vessels, corrosion and biofouling. The drifter must also accurately follow the currents in good and adverse sea states and be adaptable to follow currents at various defined depths. Finally, the instrument package must also be selfrighting in the event it is capsized by waves.